Federal and State legislation require control of vehicle exhaust emissions. Oxides of Nitrogen (NOx) are among the exhaust gas emissions that must be controlled. Formation of undesirable NOx gas will occur when there is a high combustion temperature inside of the engine. In an effort to remove or reduce combustion temperatures and NOx emissions, exhaust gas recirculation (EGR) valve systems have been developed. EGR valves function by recirculating a portion of the exhaust gas back to the intake manifold where it will be combined with incoming outside air. The mixing of the exhaust gas and the outside air will displace oxygen in the air intake system. When the mixture is compressed and ignited in the cylinder, the result is a lower combustion temperature (due to the lower levels of oxygen) and a reduction in NOx.
There is a need in the art for exhaust gas recirculation systems to reduce the number of components needed to effectively recirculate exhaust gas to the air/fuel mixture. Such systems reduce the complicated on-board plumbing of the type required for vacuum actuated EGR systems.
A typical EGR valve configuration using vacuum control uses an electrically actuated vacuum regulator (EVR) and a differential pressure sensor, also known as a delta pressure sensor. In turn, signals to and from these components are controlled by an engine control module (ECM). The effective control and simultaneous coordination of the various EGR components present some difficult challenges. More specifically, it is important to precisely actuate the EGR valve so that NOx ignitions may be optimally minimized. However, as the number of components employed in an EGR valve system increases so will the system response time. This makes it more difficult and costly to control the overall process. In related art, the EGR, EVR and delta pressure sensor are typically separate components mounted at various places on the engine and interconnected via flexible or hard conduits referred to as “on-board plumbing.” In systems presently employed in the related art, each component often requires its own mounting strategy and associated fasteners. The on-board plumbing must be routed so as not to clutter the engine. This object is not always met in EGR systems presently used in the field today it can be difficult and expensive to service. Further, and because of ever shrinking space available for the vehicle power plant, the effective use of space through efficient component packaging is a parameter which designers must constantly seek to improve.
Thus, there is a need in the art of exhaust gas re-circulation systems which reduces the number of components needed to effectively re-circulate gas to the air/fuel mixture. Further, there is a need for such a system that reduces the complicated on-board plumbing of the type required for vacuum actuated EGR systems. There is also a need in the art for an exhaust gas re-circulation system that is easy and inexpensive to service in the field. Finally, there is a need in the art for an exhaust gas re-circulation system which has improved response time and accurate repeatability and is smaller than present systems employed in the related art.